Cathode ray device



R. R. RIESZ ETAL.

CATHODE RAY DEVICE Filed May 29, 1957 QVSGR j T w June 10, 1941.

v6 Om 8 Nm Nm ERR/52 INVENTORS H & WERTZ ATTORNEY Patented June 10, 1941 CATHODE RAY DEVICE Robert R. Riesz, Mount Vernon, and Hugh S. Wertz, Forest Hills,. N. Y., assignors to Bell Telephone Laboratories, Incorporated,

New

York, N. Y., a corporation oi New York Application May 29,1937, Serial No. 145,442

12 Claims.

This invention relates to cathode ray devices and more specifically to cathode ray devices used for electrostatic recording and reproducing.

It is an object of this invention to provide a novel cathode ray device.

It is another object of this invention to provide a novel method of and means for the electrostatic recording and reproducing of signals.

It is a further object of this invention to provide a cathode ray device to record varying sig-. nals and a predetermined time thereafter to reproduce said signals.-

In Patent, No 2,200,741 issued May 14, 1940, to Frank Gray, there is disclosed a method of electrostatically recording and reproducing signals and various apparatus for producing this result. The present invention provides a compact and simple apparatus for electrostatically recording and reproducing varying signals which is an improvement on that described in the Gray patent. A feature of the present invention is that electron beams are used to both record and reproduce the signals,

In the single embodiment of this invention, which is herein described by way of example, the cathode ray device comprises a gas tight enclosure dividedinto two compartments which are separated by a common target. In one compartment, a beam of electrons which is modulated by the signals to be recorded is caused to move in a curved path in succession over one end of eachof a plurality of metallic elements mounted in said target to thereby cause the formation of charges thereon which are respectively proportional to the varying signal currents to be recorded. In the compartment or chamber on the opposite side of the target, a second electron beam is caused to move in a curved path over the opposite ends of the metallic elements in order to remove the charges produced a predetermined period of time before by the recording beam. The target preferably comprises a circular plate of insulating material which is pierced by the metallic elements arranged in a circle near the periphery of the plate. Between the periphery of the plate and the inside wall of the enclosure is placed a ring of metallic material which is preferably connected through a source of direct potential to the last accelerating anode of the gun structure for producing the electron beam used for the recording, and

through a resistance and a source of direct powhen the reproducing beam moves over each of them in turn. This resistance is also connected in the input circuit of an amplifying device in the reproducing circuit. Sweep circuits are provided to cause the beam to move in circular paths over the metallic elements and a phase shifting arrangement isprovided to keep the beams in synchronism -but out-of-phase with respect to each other. As a modification, the metallic elements may be arranged in an ellipse and the beams caused to trace elliptical paths.

The invention will be more readily understood by referring to the following description taken in connection with the accompanying drawing forming a part thereof in which:

Fig. 1 is a diagrammatic showing of a cathode ray device used for the electrostatic recording and reproducing of signals; and

Fig. 2 is a front view of the target of the device shown in Fig. 1.

Referring more particularly to the drawing, Fig. 1 shows a cathode my device In comprising in general a recording tube or compartment II and a reproducing tube or compartment l2 separated by a target l3 which is common to both. The target l3 comprises a plate of insulating material in which is inserted therethrough a circle of metal plugs 46. An input circuit is provided for the recording tube ll, an output circuit is provided for the reproducing tube l2, and circuits are provided to cause the beam in each 1 tube or compartment to move in a circle over the target l3 with a suitable phase displacement between the movements of the two beams.

The recording tube ll includes an electron gun comprising a cathode M, an anode cylinder IS, an anode plate l6, and a conducting coating H for forming and accelerating a beam of electrons and for focussing it into a fine spot upon the composite target I3. The cathode I4 is heated by a filament 18 which is supplied with current from a source of potential I9. The anode I5 is positively biased with respect to the cathode M by means of a source of direct potential 20, while the anode plate I6 and the screen H are positively biased with respect to the anode l5 by means of a source of direct potential 2!. A source of direct potential 22 may be included in circuit between the coating l1 and a metallic ring 45 the purpose of which will be more fully described below. The intensity of the beam is modulated by means of in-' coming signals applied, through the coupling condenser 23, between a modulating element 24 and the cathode l4. A high resistance 25 and biasing source of direct potential 26 are also included in this input circuit in the usual manner.

The reproducing tube I2 includes an electron gun comprising a cathode 30, a cylindrical anode 3I, a plate anode 32, and a conducting coating, 33 for forming and accelerating a beam of electrons and for focussing it into a fine spot upon the surface of the target or screen I3 remote from the recording tube II. The cathode 36 is heated by a filament 34, which is supplied with current from a source of potential 35. The cylindrical anode 3I is positively biased with respect to the cathode 30 by means of a source of direct potential 36, while the apertured plate 32 and the conducting coating 33 are placed at a positive potential with respect to the anode 3| by means of the source of potential 31. Between the metal ring 45 which surrounds the target I3 and a secondary electron collecting electrode 60 is connected an output resistance 36 and a source of direct potential 39. The resistance 33 is coupled by means of a transformer 49 to the circuit between the grid 40 and the cathode M of an amplifying device 42. A biasing source of potential 43 is also included in this input circuit.

The electron beams in the tubes I I and I2 are preferably caused to trace circular paths over the metallic plugs 46 in the composite target I3, one beam acting to form charges on one side of the target and the other beam acting a predetermined time thereafter to remove these charges. While it should be understood that separate sources for the deflecting voltages may be provided to control the movement of the cathode ray beams in the respective tubes I I and I2, it is preferred to supply the deflecting voltages from a single source of oscillations in order to interlock the movements of the two beams. The oscillator 50 preferably supplies waves of sinusoidal form which are applied to the pairs of deflecting plates I and 52 of the tube or compartment I2 through a resistance 53 and .a condenser 54 connected in series with the oscillator 50. These impedance elements serve as a phase splitter for obtaining quadrature voltage components of the output of the oscillator 50 which components are applied to the respective pairs of deflector plates 5I and 52.

Also connected in series with the oscillator 50 is a phase shifter 55 which may be any one of a variety of well-known forms and is preferably so constructed that the amount of the phase shift may be adjusted. The output of the phase shifter is applied across a resistance 56 and a capacity 51 connected in series. These latter impedance elements serve as a phase splitter for obtaining quadrature voltage components which are applied to the respective pairs of deflector plates 58 and 59 The value of the voltage delivered by the oscillator and the values of the resistance and capacity elements 53, 54, 56 and 51 are preferably so adjusted that the beam in the tube II traverses a circular path over one end of each of the metallic elements 46 and the beam in the tube I2 traverses a similar circular path over the opposite end of each of these metallic elements but a predetermined time thereafter, this time interval being determined by the amount of the phase shift produced by the phase shifter 55 and the frequency of oscillations generated by the oscillator 56.

The operation of the device shown in Fig. 1 will now be described. A cathode ray beam in the tube II is formed and accelerated by the cathode I4 and the anodes I5, I6 and I1 and is focussed into a fine spot on the target I3 by means of the electron lens action of the anodes. This beam is modulated in intensity by incoming signals which are applied between the modulating element 24 and the cathode I4. The modulated beam is caused to move in a circular path successively over one end of each of the metallic elements 46 to cause the formation of charges thereon which vary in accordance with the variations in the incoming signals. If the incoming signals are voice currents, the charges formed successively on the metallic elements 46 vary in accordance with the variations in the voice of the speaker but if the incoming signals are currents from a picture transmitting or television transmitting station, the charges upon the successive elemental metallic elements 46 vary in accordance with the light-tone values of the successively scanned elemental areas of the object at the transmitting station. The charges will be held on the metallic elements 46 because of the condenser action between the elements 46 and the metallic ring which ring is separated by a narrow ring of insulating material 41 from the elements 46 (see Fig. 2). If desired, the ends of the metallic elements 46 in the tube Il may be coated with a suitable substance such as, for example, carbon to prevent or decrease secondary emission. The electrons in the beam which are not laid down on the metallic elements 46 are collected by the conducting coating I1. In the cathode ray tube or compartment I2 an electron beam is formed and accelerated by the cathode 30 and the anodes 3|, 32 and 33, and is focussed into a fine spot on the target I3 by the electron lens action of the anodes. This beam is also caused to move in a circle over the ends of the metallic elements 46 remote from the tube II by the quadrature voltage components applied to the deflecting plates 5I and 52. Due to the action of the phase shifter 55, the beam in the tube I2 which lag behind the beam in the tube II by a predetermined phase. angle, depending upon the amount of the phase shift produced in the device 56. In order to obtain the maximum time delay, this phase shift may amount to almost 360 degrees. The amount of time delay between the signals applied to the input circuit of tube II and the reproduced signals in the output circuit of tube I2 depends upon the period of time taken for one complete revolution of the beam and upon the angular amount of the phase shift produced by the device 55.

By the present theory of operation of this device, the negative charges applied to the metallic elements 46 by the beam in the tube II are removed by the electron beam in the tube I2 by secondary emission action. The voltages applied to the anode members in the tube I2 and the material of the metallic elements 46 are chosen so that more secondary electrons are emitted than there are primary electrons in the beam. The elements 46, for example, may be made of nickel, or they may be made of any good conducting metal and coated with a suitable alkaline'earth oxide layer to enhance the emission of secondary electrons. The secondary electrons are collected by the electrode member 60, thus removing the charges from each metallic member in turn As the charges are removed from the metallic elements 46 which'are successively contacted by the beam in the tube I2, a succession of surges is set up in the resistance 38 which is representative of the incoming signals in the input circuit of the tube ll displaced in time by a predetermined amount. The reproduced signals are amplified by the device 42 which may be, if desired, multistage, and then applied to a suitable translating device, such as a telephone receiver or a television receiving apparatus. The source of potential 39 which is connected in series with the resistance 38 between the ring and the collecting electrode is preferably so poled that the collecting electrode 60 is at a positive potential with respect to that of the metallic elements 46 in order to encourage secondary emission from these elements to the electrode 60. The potential of this source and of the potentials applied to the accelerating anodes are so chosen that the desired amount of secondary electrons is removed. For proper operation only those charges which are placed on theelements 46 by the electron beam in the tube II are removed by secondary emission in the tube l2. After the charges have been removed from the metallic elements 46 these elements remain uncharged at this original or equilibrium potential until the beam of the tube ll passes over is easily adjustable as the output signals maybe delayed from the input signals by a time interval that can be made any fraction of the time of one revolution of the electron beam. It is electron beams over said conducting portions in the same order.

2. In combination, a screen comprising an insulating plate. containing a plurality of conducting portions, said conducting portions being arranged in a circular path, and means for generating and moving two electron beams over said conducting portions in the same order.

3. The combination with a conductive element having one portion thereof a poorer emitter of secondary electrons when bombarded by electrons than a second portion thereof, said element piercing an insulating member, of means for bombarding said portions alternately with electrons, and means for utilizing the secondary electrons emitted from said second portion to set up an electric current.

suitable for frequencies much above the upper frequency limit of the telegraphone which limit lsgenerally of the order of 5000 cycles although the time delay of signals of higher frequency ranges will be limited by the number of metallic nents may be arranged in rows and the cathode ray beam caused to scan each of these rows in mm as in the well-known television transmit- ;ing and receiving systems employing cathode ray devices. This last modification makes possible the use of a great deal more metallic elenents 46 without having larger tubes. In this arrangement, the metal ring 45 is replaced by a. nesh grid electrode imbedded in the insulating naterial of the target l3, the elements 46 being .nserted between the interstices of the mesh. I

Other modifications may be made in the 'arrangenint as above described without departing from the spirit or principles of the invention as ;herein expressed, the scope of which is defined 1y the appended claims.

What is claimed is:

1. In combination, a target comprising a plate if insulating material, and a plurality of conucting portions in said insulating material, said mducting portions being arranged in a curved ath, and means for generating and moving two 4. The method of varying the potential of an insulated conductive element which comprises bombarding it with electrons to impart a negative charge thereto, non-concurrently therewith bombarding it with electrons so as to set up secondary electron emission therefrom and preventing released secondary electrons from returning to said element by the application of an electric field.

5. In combination with a cathode ray device having means for generating and deflecting two electron beams, a source of oscillations, means for applying current from said source of oscillations through a resistance and capacity in series,

means for applying the impedance drop across.

said resistance and capacity to respective pairs of deflecting plates associated with one electron beam, 9. phase shifting arrangement the input of which is in series with said resistance and capacity, a second resistance and capacity in the outputl circuit of said phase shifter, and means for ap lying the impedance drop of said second resistance and capacity across respective pairs of deflecting plates associated with said second electron beam.

6. A composite target comprising a layer of insulating material, a row of metallic elements arranged in a circle near the periphery of said insulating material, a carbon coating for one end of each of said metallic elements, and a metallic ring locatedaround the periphery of said insulating material. '7. A cathode ray device for electrostatic recordmg and reproducing comprising two gas-tight envelopes separated by a target common to both, said target comprising a plate of insulating material pierced with a plurality of conducting elements located in a circular path near the periphery thereof, and a ring of metallic material around the periphery of said insulating plate, one of said envelopes enclosing means for generating a beam of electrons, means for modulating said beam in accordance with incoming signals, and means for deflecting said beam in a circular path over said metallic elements one by one in succession, and said second envelope enclosing means for generating a beam of electrons, and means for deflecting said beam in a circular path over the ends of the metallic element remote from said first envelope.

8. A composite target for a beam of electrons comprising a layer of insulating material, a row of metallic elements arranged in a curved path near the periphery of said insulating material, and a metallic ring located around the periphery of said insulating material.

9. A composite target for a beam of electrons comprising a layer of insulating material, a row 01 metallic elements arranged in a curved path near the periphery of said insulating material, a carbon coating for one end of each of said metallic elements, a coating of a material that emits secondary electrons freely when impinged upon by primary electrons for the other end of each of said metallic elements. and a metallic ring located around the periphery of said insulating material.

10. A composite target for a beam of electrons comprising a layer of insulating material, a row of metallic elements arranged in a curved path near the periphery of said insulating material, said metallic elements being of material which is a good emitter of secondary electrons, and a metallic ring located around the periphery oi the entire layer of said insulating material.

- 11. In combination with a cathode ray device having means for generating and deflecting two electron beams, a source of oscillations, means for deriving from said source or oscillations deflecting voltages to apply to the means for deflecting one of said beams to cause said beams to move in a closed path, means for deriving from said source potentials to apply to the means for deflecting said second electron beam to cause said second means to be deflected in a closed path, and means for adjusting the phase 01 themovement of said electron beams with respect to. each other. on 4 12. In combination, a screen comprising an insulating plate containing a plurality of conducting portions, said conducting portions being arranged in an elliptical path, and means for generating and moving two electron beams over said conducting portions in the same order.

ROBERT R. RIESZ. HUGH S. WERTZ. 

